Embodiments of the inventive concepts described herein relate to high-resolution imaging technologies of improving resolution of a three-dimensional (3D) medical image based on bone remodeling simulations and reconstructing a skeletal image as a high-resolution image.
A prevalence rate of osteoporosis of domestic people who are older 50 is very high to have 34.9% of females and 7.8% of males. Globally, about 200 million women suffer from osteoporosis now. For example, 10% of women over 60, 20% of those over 70, 40% of those over 80, and 75% of those over 90 are affected for each age. In addition, the prevalence rate of osteoporosis is steadily increasing as society ages.
Osteoporosis represents a state of a high possibility that fractures will occur since bone strength is weak due to reduced bone mass and a qualitative change. Herein, the bone strength may refer to a force in which a bone resists its fracture. This is determined by ‘bone mass’ and ‘bone quality’.
Osteoporosis finally causes osteoporotic fractures by reducing bone mass and weakening bone quality. The osteoporotic fractures cause enormous economic damage as well as degrade the quality of personal life by accompanying complications together with a serious mobility impairment. For example, according to research by the Unites States, medical costs by osteoporotic fractures are $18 billion every year. It is very important to perform an early diagnosis through skeletal medical images since this osteoporosis has no special subjective symptoms. However, after 30% to 50% of most bone mass is lost, people realize that they suffer from osteoporosis due to the occurrence of fractures by external impacts. As such, late realization for osteoporosis results in a high fatality rate and serious sequelae. A trabecular bone network cut once may not be restored to a previously connection state by medical treatment due to irreversibility of ‘bone remodeling’ using current medical technologies. In addition, assuming that there is the same bone mass loss, since a decrease in connectivity of trabeculae has more influence on bone strength than a decrease in thickness of the trabeculae, it is very important to maintain connectivity of bone microstructures. In other words, it is clinically important to perform an early diagnosis of osteoporosis.
In general, the diagnosis of osteoporosis is indirectly made by measuring bone mineral density (BMD). Dual energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT), and the like are used as representative BMD measurement methods. The DXA is to measure average BMD for a volume of interest (VOI) of a lumbar spine and a femur, to obtain a T-score for average BMD of a healthy adult, and to perform diagnosis of ‘normal (T≥−1.0)’, ‘osteopenia (−1.0≤T≤−2.5)’, and ‘osteoporosis (T≤−2.5)’ based on the BMD T-score. The DXA is the most widely used in the world today due to a short measurement time, a low amount of radiation, a low measurement cost, and the like. However, the DXA obtains only ‘bone mass’ information based on an X-ray attenuation difference, but does not provide information about ‘bone quality’ such as a bone microstructure of a trabecular bone. Due to absence of information about a bone microstructure, if two objects having different bone microstructures (herein, it is assumed that genders, ages, and the like are the same as each other) have the same average BMD value, there is a situation of giving the same diagnosis of osteoporosis irrespective of different bone strength. In other words, a possibility of misdiagnosis is always present. A fracture risk assessment tool (FRAX) is provided as a method for solving the problem of the DXA and is attempted to perform clinical application.
Since bone strength is determined by a structure of a trabecular bone as well as BMD, a method of simply measuring only BMD may predict only 64% of mechanical bone strength, but may predict 94% of the mechanical bone strength in case of considering a 3D structure. In other words, it is essential to perform a quantitative structure analysis for a trabecular bone for the reliable early diagnosis of the osteoporosis. If BMD measurement is combined with a bond structure analysis, it is possible to perform a more accurate diagnosis of osteoporosis. Quantitative estimation for bone strength is recently attempted by linking high resolution peripheral QCT (HR-pQCT) which may capture bone microstructures to a finite element analysis. In the HR-pQCT, there is a limitation that it is impossible to capture a significant lumbar spine and femur in the diagnosis of osteoporosis.
A medical imaging device plays an important role in the diagnosis and treatment of disease by imaging information about a human body in a quantitative manner. Computer tomography (CT) and magnetic resonance imaging (MRI) are the best examples of the medical imaging device. In case of CT and MRI, a signal detector decreases in size to obtain a high-resolution image to increase the number per unit area. However, since a current maximum resolution is an in-plane resolution of 0.2×0.2 mm2, it is impossible to capture a bone microstructure. In addition, it is possible for recently developed HR-pQCT to obtain a high-resolution image (an image with a level of 50 μm) and to have a limitation in a capturing portion such as a wrist and an ankle. As described above, it is impossible to capture a femur or a lumbar spine which is a diagnosis portion of osteoporosis.
There is a method of solving a hardware-like limitation of this medical imaging device by softwarily accessing the medical imaging device. For example, image processing such as compressed sensing for an image captured by the medical imaging device is performed, and an original image is reconstructed based on some extracted data. In addition, there is a super resolution processing method performed in image post-processing. However, in case of an image processing method such as compressed sensing and super resolution, it is possible to perform any high-resolution imaging of medical images, but there is a limitation that the image processing method does not provide a high-resolution image of a degree to analyze a 3D microstructure.
Thus, there is a need for high-resolution imaging technologies of performing local high-resolution imaging for a low-resolution image based on bone remodeling simulations to verify a bone microstructure. Korean Patent No. 10-1531654 discloses technologies of reconstructing a 3D image by improving a convergence speed using compressed sensing.